3000g Aquarium Bio Ceramic Rings in 6 Media Bags for Fish Canister Filter Aquarium Accessories Extremely porous ceramic media for efficient biological filtration. Their surface area and pores are sized to accommodate bacteria necessary for biological balance and to remove toxic ammonia and nitrite. Hollow design effectively distributes water flow and allows massive colonies of beneficial bacteria to grow on and inside each ring, creating an ideal bio chemical filter. They will not break down in the filter or alter pH or water hardness. Great for both fresh and saltwater aquariums Free media bag for easy handling. The zipper-design media bag is reusable.